1. Field of the Invention
The invention herein relates to improvements in and relating to wheeled chairs for the non-ambulatory or those with limited ambulatory function, and more specifically to wheeled chairs that are capable of vertical movement, thereby adding to the functionality of the user in day to day activities which involve interaction with objects of various heights.
1. Overview of Prior Art
A variety of art exists in the area of wheeled chairs but the art is filled with devices that have truly limited functionality. For a person in a wheel chair, stooping down to pick up a fallen object or to retrieve something off of a shelf or cabinet is difficult if not impossible without getting out of the chair. For many this is not an option. As a result chairs that involve vertical movement have been developed, but with only limited success. Higgs, in U.S. Pat. No. 4,477,117, disclosed such a chair. Here a folding wheel chair is disclosed with a pair of vertically slidably mounted guides and an elevation means to vertically displace the seat and back rest on a supporting frame. While such a device might seem plausible, the excessive manufacturing expense of the low friction linear movement mechanism that can be feasibly driven by a motor and screw mechanism is simply not practical. The energy loss to friction would dictate a heavier, more powerful motor and if the device is to be powered by a battery, the limited life or extra weight of additional batteries make the product undesirable.
Linear movement is also used in the telescoping back frame of U.S. Pat. No. 5,094,508 as disclosed by Bathrick et al. Here the function of the device is only to assist the user in getting out of the chair by raising the rear of the seat and pivoting the front. The device is not fitted with wheels of any kind and the device is disclosed with a cord to provide power to the motor. This cord necessitates the chair be virtually immobile even if wheels were fitted onto the frame. As such, the torsion of the actuator and the eccentric load placed on the telescoping members would indicate high friction losses and limit the efficiency of the system.
Mechanical methods of vertical displacement are also disclosed. The first, by Pearce, Jr. in U.S. Pat. No. 5,423,562 uses a mechanical crank to elevate a chair which, again is slidably mounted onto the frame. The lack of physical strength of an injured or aged population, the majority of which would be using such a device, would preclude them from using such a device, therefore another person must adjust it for them. In addition the device must be entered from the rear or by stepping over the sides of the chair, making entry difficult if not impossible for those with ambulatory restrictions.
The second such mechanically adjusted device was disclosed by Branscumb et al. in U.S. Pat. No. 5,060,960 in which a hydraulic jack is used to vertically displace a slidably mounted seat on a wheeled chair. As before, a second person is required to actuate the device, which here is understandable in that the device is intended to facilitate the transfer of the user to and from a bed. Many times these users have very limited physical abilities and therefore require assistance. This necessitates another person be present to assure safety in making the transfer. This device is primarily intended to assist the attending person, not the user seated in the chair.
Gaffney in U.S. Pat. No. 4,083,599 disclosed an overstuffed rocking chair that could be fitted with wheels that includes a linkage mechanism and a actuator to vertically displace and tilt the chair to facilitate entry and exit from the chair. Not only is the chair intended to assist in exiting the chair and not functional use at different heights, but the physical size of the chair makes it very limited in mobility. In addition, the wheels are disclosed as being fit onto the frame, separate from the lift mechanism, thereby disengaging the wheels from the ground when the lift mechanism has been actuated. This obviously precludes translation of the device and user at any height other than at the fully retracted position making the device nonfuctional as a variable height wheeled chair.
A wheeled commode is disclosed by DeWeese in U.S. Pat. No. 5,161,812. Here as with Branscumb et al. the device is lifted by a hand powered hydraulic ram for the purpose of assisting in patient transfer. A linkage mechanism is used to vertically displace the seat but four slidably mounted tubes are used to guide the movement. The linkage design is not desirable in this case because the load applied to the ram, and therefore the user physically actuating the ram, is great at the bottom position of the seat and gradually decreases as the seat moves upward. Also fluid power systems such as these disclosed have a tendency to leak over time. This is not only messy but potentially dangerous, having spilled oil on the floor of a hospital or any other environment with people of limited physical capability.
A seat with a linkage provided to lift the seat was disclosed in U.S. Pat. No. 3,596,982 to Grams. This is a patent chair such as would be used by a patient of a dentist. Mobility of the chair is not disclosed nor desirable in that the chair is intended to manipulate the patient into various positions to better enable the practitioner to perform his duties. The device is to heavy and cumbersome to be used in any manner of locomotion even if wheels were affixed thereto.